The invention relates to skin cosmetics.
Skin cosmetics are generally designed to give skin a more youthful, healthy appearance. One aspect of this goal is reducing the visibility of wrinkles and eliminating oily glare. Most existing skin cosmetics are creams or powders which, when applied to skin, create an opaque layer which hides wrinkles and diffuses reflected light. Covering skin with an opaque substance, however, can give skin a homogenous, unnatural appearance.
The invention is based on the discovery that if a cosmetic layer or coating is applied to skin that specifically reduces the Fresnel component of reflectance, without affecting other skin optics parameters, the coating will obscure wrinkles and give the skin a more natural, youthful appearance. In addition, by including in a skin cosmetic colored additives that mimic natural chromophoric structures in skin, the overall appearance of the cosmetic will be more lifelike and natural.
In general, in one aspect, the invention features an anti-reflective cosmetic composition for skin. The composition includes a material that, when applied to skin, forms a layer of the material that adheres to the skin, has a thickness of from about 60 nm to about 140 nm and a refractive index of between about 1.1 and 1.4. The layer reduces the Fresnel component of light reflected from skin.
Embodiments of this aspect of the invention can include one or more of the following features. The layer has a thickness of between about 80 nm and 120 nm, e.g., 95-100 nm, and a refractive index of between about 1.2 and 1.3, e.g., 1.22. The layer can be a molecular monolayer including amphipathic molecules, such as straight-chain phospholipids. The amphipathic molecules can have lengths of between about 95 nm and 100 nm. In addition, the layer can include a trapped gas to reduce the index of refraction of the layer. The trapped gas can be in one or more microspheres or microbubbles having diameters less than about 55 nm. The composition can also include a carrier, such as water.
Alternatively, the molecular monolayer can include a monomer, where the monomer, when activated, polymerizes to form the molecular monolayer. The monomer includes a negatively charged moiety, such as an amine group or a carboxyl group, that is attracted to stratum corneum. Activation of the monomer can be triggered by application of the material to skin. The cosmetic composition can also be an aerosolizable liquid that can be sprayed onto skin to form the layer.
The cosmetic composition can further include a chromophore having a natural skin color. The chromophore can be, e.g., melanin granules or liganded hemoproteins. The layer formed by the composition can be generally translucent or transparent.
Instead of a molecular monolayer, the layer can be, e.g., a monolayer including a trapped gas to reduce the refractive index. The trapped gas can be in one or more microspheres or microbubbles. The layer can include microspheres and can further include a packing agent. The packing agent is, e.g., a polymer such as polyvinylalcohol, polymethyl methacrylate, polydimethyldiallylammonium. The microspheres can be encapsulated by a capsule substance having a negatively charged moiety, such as a polycarbonate group.
In another aspect, the invention features a method of reducing Fresnel reflectance from skin. The method includes applying a cosmetic composition to skin, such that a material in the composition forms a layer on the skin. The layer has a thickness of between about 60 nm and 140 nm and a refractive index of between about 1.1 and 1.4.
Embodiments of this aspect of the invention can include one or more of the following features. The layer is a monolayer. The composition includes a carrier, and the method further includes removing carrier and non-bound material from the skin, e.g., by washing or allowing the carrier to evaporate after formation of the monolayer, such that only the monolayer remains on the skin.
In another aspect, the invention features a cosmetic composition having colored, shaped additives that mimic the appearance of colored structures in healthy skin and a carrier. The additives are mixed into the carrier in an amount sufficient to mimic spectral texture of healthy skin when applied to the skin.
Embodiments of this aspect of the invention can include one or more of the following features. The carrier can include a chromophore having a natural skin color, e.g., the color of melanin or oxyhemoglobin. The colored structures mimicked by the additives can be mimics of natural structures in skin such as hair follicles, sweat duct openings, fine hairs, freckles, or blood vessels. The additives can be dyed polymers, and have shapes such as threads, disks, or beads. The composition can further include a material that forms a layer when the material is applied to skin. The layer has a thickness of between about 60 nm and 140 nm and a refractive index of between about 1.1 and 1.4.
An xe2x80x9camphipathic moleculexe2x80x9d is a molecule having a polar end and a lipophilic end.
As used herein, xe2x80x9cspectral texturexe2x80x9d describes the spatial variation in the reflectance spectrum caused by endogenous skin pigments localized in structures such as blood vessels, freckles, vellus hairs, pores, and follicles.
As used herein, a microsphere is a small sphere of a capsule substance, e.g., albumin or a natural or synthetic polymer, that surrounds a gas. A microbubble is a small pocket of gas within a solid or liquid.
Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Although methods and materials similar or equivalent to those described herein can be used in the practice or testing of the present invention, suitable methods and materials are described below. All publications, patent applications, patents, and other references mentioned herein are incorporated by reference in their entirety. In case of conflict, the present specification, including definitions, will control. In addition, the materials, methods, and examples are illustrative only and are not intended to be limiting.
The new cosmetics provide the advantage of reducing the visibility of wrinkles and coarse details in skin without affecting other skin optics parameters, such as spectral texture and color, to give the skin a more natural, youthful appearance. The anti-reflective cosmetics are non-toxic and are easy to apply. In addition, the new cosmetics that include colored additives allow wrinkles and skin blemishes to be obscured, without making the skin appear homogenous and unnatural. Sunscreens and moisturizers can easily be added to the new cosmetic compositions.
Other features and advantages of the invention will be apparent from the following detailed description, and from the claims.